To enhance or increase the production of oil and gas hydrocarbons from wells bored into subterranean-formations, it has been common practice to pump a viscous fluid at high pressure down into the well bore to crack the formation and force the fracturing fluid into those cracks. The fracturing fluid is also used to carry sand or other types of particles, called proppants, to hold the cracks open when the pressure is relieved. The cracks held open by the proppant provide additional paths for the hydrocarbons, such as oil or natural gas, to reach the wellbore, which, in turn, increases the production of oil and/or natural gas from the well.
However, while recovering these hydrocarbons, the process of water flooding is used in the petroleum industry to increase the recovery of oil. This process increases the total yield of oil present in a formation beyond what is usually recovered in the primary process. It is desirable in this process to maintain a high rate of water injection with a minimum expenditure of energy. Any impediment to the free entry of water to oil-bearing formations seriously reduces the efficiency of the recovery operation.
However, water flooding systems provide an ideal environment for growth and proliferation of biofilms due to the large amount of water being transported through these systems and injected into oil bearing formations in an effort to maintain reservoir pressure and/or to increase the mobility of oil through the formation to producing wells. The large surface area of the water distribution network encourages biofouling, which is the attachment and growth of microbes and/or bacteria on the pipe walls.
Biofouling caused by anaerobic bacteria is compounded in water floods by the practice of removing oxygen from the water before injection. The removal of oxygen is done to minimize corrosion of equipment; however, the anoxic conditions provide an ideal environment for the growth of sulfate reducing bacteria (SRB) in the biofilms. This phenomenon is observed both on the injection side and producing side of the water flood operation. The metabolic activity of these bacteria can lead to accelerated corrosion rates, plugging of filters, health hazards from the sulfide production, and eventual souring of the formation (a sour well contains hydrogen sulfide).
One method to control biofouling is to apply a biocide. The biocide is generally selected based on its performance in a standard laboratory evaluation test. However, the present application is directed to an encapsulated biocide. Prior to the present application, non-encapsulated biocides possessed multiple short comings. For example, non-encapsulated biocides, when released or pumped into the wellbore, may possess a foul odor. Furthermore, once a non-encapsulated biocide is placed into the wellbore, the biocide may potentially react with other components, such as friction reducers and other additives, in the wellbore fluid. Additionally, non-encapsulated biocides are often in liquid form and thus must be pumped with suitable equipment by personnel on the wellbore site, which inherently possesses numerous health, safety and/or environmental concerns.